How to Fix a Space Toilet

Following the first of three spacewalks at the International Space Station, astronauts will get down to work Wednesday to fix what has produced an uncomfortable situation for the crew: the broken toilet.

When Discovery docked at the International Space Station Monday afternoon, the station's three crew members were ready to welcome their colleagues – and the spare parts they were bringing to fix the toilet.

Shuttle Commander Mark Kelly opened the hatch and joked, "Anyone here call for a plumber?"

Space Station Flight Engineer Garrett Riesman responded, "We thought you all were on a lunch break. What took you so long?"

An orbiting toilet, for lack of gravity, uses fans to pump waste into storage tanks. One system, for solid waste, has worked fine; the liquid-waste system stopped with a bang last month.

It turned into a headache for Reisman and Russian cosmonauts Sergei Volkov and Oleg Kononenko, who could not get it working with the spare parts they had on board. They were spending a couple of hours a day working a manual pump to keep the system going.

Volkov will be the actual plumber on Wednesday, installing a new pump that was brought up on Discovery. There is only one bathroom on the space station, in the Russian segment, and it has gone through three pumps in the past one-and-a-half weeks. Everyone hopes this brand-new pump — from a different manufacturing batch — will finally fix the problem.

Space Station Preps NASA for Mission to Mars

"It's just another day in the life of operating an International Space Station," says program manager Mike Suffredini of such glitches. When headaches like broken plumbing arise, it's his problem.

The space station is a work in progress, and one reason for its existence is to learn how to live in space for long periods of time. Solar arrays break and computers break; the crews can (and have) run low on food and water.

It teaches NASA important lessons: how to fix a problem on the fly if a crew is ever sent on a three-year mission to Mars.

Suffredini explained this philosophy to ABC News in an interview last year.

"Human research will continue the on space station, which will help us decide what we need to do to protect the crews to go for long trips in outer space," he said at the time. "The other thing is the systems checks because a lot of systems are going to have to operate at a very low-gravity environment and we can test that on the space station."

In addition to toilet repair, Discovery's crew will install the billion-dollar Japanese Kibo module on the nine-day mission.